>>>>This server has been in use since 2008
>>>>Suddenly today, rows disappear.
>>>>It might be a coincidence, but the rows seem to be disappearing after a backup occurs.
>>>>Many backups have been made before with no issues.
>>>>Any ideas?
>>>
>>>The question is unclear. Did you find some table(s) missing rows? If yes, how did you find it? Is it possible that these rows were deleted? Do you have any audit in place?
>>
>>Run a report
>>Rows are there
>>Back up the system
>>Run a report
>>Rows are gone
>>No audit
>
>1. Examine the backup job
>
>2. In SSMS run the query that drives the report. Perhaps some parameters have changed.

I think I have a good candidate for the solution.
The clue was that some research showed that only rows in one table were missing.
The VFP program that created those rows had not committed the transactions in question when the backup was made.
I changed that.
I'll see if that was the issue.